水溶性和碱溶性蔗渣木质素的分离与表征

以蔗渣为原料，经脱蜡后依次用H₂O、1% NaOH和3% NaOH进行抽提，分别得到水溶性木质素L1和碱溶性木质素L2、L3，并对其理化性质和结构特征进行分析。通过硝基苯氧化法、高效液相色谱检测来确定蔗渣木质素的组分，通过凝胶渗透色谱检测蔗渣木质素的分子质量，利用紫外分光光度计和二维核磁共振推导出蔗渣木质素的结构单元和连接方式。结果表明，L1、L2和L3的得率（以绝干原料计）分别为0.4%、5.7%和3.7%，占蔗渣木质素总量的54.1%，而且水溶性木质素分子质量大于碱溶性木质素。L2和L3主要来自于蔗渣次生壁，富含紫丁香基单元和大量的非缩合醚结构。蔗渣木质素的结构单元间的主要连接方式是β-O-4'醚键，还有β-β'、β-5'和β-1'等碳碳结构。蔗渣木质素是由紫丁香基、愈创木基和少量对羟苯基结构单元组成的GSH型木质素，此外，还含有对香豆酸和阿魏酸，通过酯键与木质素相连。

Isolation and Characterization of Water-soluble and Alkali-soluble Lignin from Bagasse

The lignin fractions(water-soluble lignin L1 and alkali-soluble lignin L2, L3)were extracted by H₂O, 1% NaOH and 3% NaOH aqueous solution from the dewaxed bagasse. The components of three lignin fractions were analyzed by nitrobenzene oxidation and high performance liquid chromatography, the molecular weights were detected by gel permeation chromatography, and the structure units and linkages were studied by UV and 2D HSQC NMR. The results reflected that the yields of L1, L2 and L3 were 0.4%, 5.7% and 3.7%, and they occupied 54.1% of the original lignin.And the molecular weight of water-soluble lignin was higher than that of alkali-soluble lignin. Furthermore, the L2 and L3 were from the secondary wall of bagasse and the dominating constituents of them were syringyl units and large amounts of noncondensed ether structures. The lignin structural units were linked to each other mainly by β-O-4' ether bonds, β-β', β-5', β-1'. And the lignin was GSH lignin composed by syringyl, guaiacyl and little p-hydroxylphenyl units. The linkage between p-coumaric and lignin was ester bond, whereas the linkages between ferulic acid and lignin were both ether and ester bonds.